In general, a gear box for use in an opening/closing structure, such as a conventional digital door lock, should transmit a rotational force to a dead bolt, which is means of opening/closing mean the digital door lock when a motor itself is rotated. However, when the dead bolt is manually operated, the rotation force should not be transmitted to the rotation shaft of the gear box in order to protect the driving circuit of the motor connected to the rotation shaft and an internal speed reduction gear accommodated in the gear box.
This function is usually called an anti-panic function, and various types of gear boxes having the anti-panic function have already been on the market. Since the anti-panic function of a gear box makes the structure of the gear box complicated, which increases costs, a gear box, which has an anti-panic function and is economic and simple in structure, is required.
In order to meet such a requirement, Korean Utility Model Registration No. 20-0452407 (entitled “Gear Box with Anti-Panic Function”) discloses a gear box having an anti-panic function. The gear box having the anti-panic function prevents the rotation of a rotation shaft of the gear box when rotation force is applied from the outside so that a motor driving circuit and internal speed reduction gears accommodated in the gear box can be protected.
However, the conventional gear box has problems in that since a plurality of speed reduction gears are used for connection, a large force is needed when a user manually rotates the gear box and the gear box is complicated in structure.